(a) Field of the Invention
The present invention relates to a manufacturing method of a three-dimensional structure having a hydrophobic external surface, and more particularly, to a three-dimensional structure manufacturing method for performing surface treatment processes and a replication step to provide hydrophobicity on an external surface of the three-dimensional structure.
(b) Description of the Related Art
Generally, a surface of a solid body formed of a metal or a polymer has an inherent surface energy, which is shown by a contact angle between the solid body and a liquid when the liquid material contacts the solid material. The liquid may include water, oil, and so forth, and hereinafter, water will be exemplified as the liquid. When the contact angle is less than 90°, hydrophilicity in which a sphere shape of a water drop is dispersed on a surface of the solid body to wet the surface is shown. In addition, when the contact angle is greater than 90°, hydrophobicity in which the sphere shape of the water drop is maintained on the surface of the solid body to run on the surface is shown. Aa an example of hydrophobicity, a water drop that runs on the surface of a leaf of a lotus flower flows without wetting the leaf.
Further, when the surface of a solid body is processed so as to have slight protrusions and depressions, the contact angle of the surface may vary. That is, when the surface is processed, the hydrophilicity of a hydrophilic surface with a contact angle that is less than 90° may increase, and the hydrophobicity of a hydrophobic surface with a contact angle that is greater than 90° may increase.
The hydrophilic surface or the hydrophobic surface of the solid body may be applied to various products of a three-dimensional shape. Particularly, since the liquid may not wet the hydrophobic surface and it may easily flow by external force, the amount and the speed of the liquid may increase, and therefore the hydrophobic surface may be applied to various products of a three-dimensional shape.
That is, when the hydrophobic surface is applied to structures such as a torpedo, a submarine, and a ship, flow resistance applied to an outer surface of the structure may be reduced. Accordingly, the structure having the hydrophobic surface may go faster with the same impellent force than a conventional structure. Further, since a flowing speed is high on the hydrophobic surface of the structure, foreign materials may not be accumulated on the surface.
In addition, when the hydrophobic surface is applied to an external surface of a structure such as a vehicle, air resistance may be reduced compared to a conventional structure. Therefore, a vehicle having the hydrophobic surface may go faster with same impellent force than the conventional structure.
Technology for applying the hydrophobic surface to the structure of the three-dimensional shape has depended on a microelectromechanical system (MEMS) process applying a semiconductor fabrication technology. The MEMS process is an advanced mechanical engineering technology applying semiconductor technology. However, the apparatus used for the semiconductor process is very expensive. In order to form the nano-scaled protrusions and depressions on a surface of a solid metal body, a variety of processes that cannot be performed under a normal working environment such as a process for oxidizing the metal surface, a process for applying a constant temperature and a constant voltage, and a process for oxidizing and etching using a special solution, must be performed. That is, in order to perform such processes, a specifically designed clean room is required and a variety of expensive apparatuses for performing the processes are necessary. Even though the hydrophobic surface has various merits, it has not been widely used because of a manufacturing limit of the hydrophobic surface.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.